1. Field of the Invention
This invention relates, generally, to disposable, field usable detectors for detecting the presence of substances in test fluids by use of indicator chemistry. More specifically, this invention relates to single-use, disposable devices for efficiently detecting the presence of controlled or other substances in the breath or other fluid by employing chemical indicators that react in a certain prescribed manner to the presence of such substance.
2. Description of the Prior Art
U.S. Pat. No. 4,740,475, awarded Apr. 26, 1988 to Paul, discloses an alcohol detection device that addresses the problem of “chemical indicator freshness.” The indicator reagents typically used in these devices tend to deteriorate when exposed to air or moisture prior to use. Thus, the devices have to be handled and stored carefully. The reliability of these types of tests is questionable in the event of breakage or improper sealing.
However, the potential ease of use and reliability of low-cost, throw-away substance detectors using indicator reagent chemistry has continued to encourage researchers to develop a method of insuring the freshness and integrity of the indicator reagents to increase the accuracy and reliability of the tests. Various units and cartridges have been developed containing plugs and seals in an effort to assure indicator reagent freshness.
For example, the detector device shown in the Paul patent has a flexible, deformable housing that forms a test chamber for interacting an indicator reagent with the sample fluid. A rupturable ampoule containing an indicator reagent is positioned within the housing. The indicator reagent completely fills the ampoule and the diameter of the ampoule is only slightly less than the diameter of the lumen of the deformable housing.
Two porous plugs, located at opposing ends of the ampoule, maintain the position of the ampoule within the housing. To use the device, a user ruptures the glass ampoule through application of a predetermined pressure through the walls of the deformable housing. The user then blows through the opening at one end of the device, causing the breath to be exposed to the indicator reagent that has been introduced into the chamber by the breaking of the ampoule. In the presence of the predetermined substance in the sample fluid, the indicator reagent undergoes a known change in color.
The Paul device is characterized as being portable. However, the glass ampoule is easily broken if the device is carried in a pocket or other relatively unprotected container. Thus, the device is portable only when carefully transported.
There is almost no space between an outer housing of vinyl and the glass ampoule therewithin. Thus, the device is extremely fragile, easily broken, and thus is not truly portable. Moreover, the absence of space between the vinyl housing and the glass ampoule can result in cut fingers when the housing is squeezed to break the ampoule.
Thus there is a need for a truly portable detector having enhanced safety features.
Moreover, the ampoule is completely filled with the indicator reagent. This offers significant resistance to fluid flow. Thus, there is a need for an improved detector with less resistance to fluid flow so that a user need not blow as hard as when using the Paul device.
A considerable amount of force may be required to crush the Paul ampoule. A need exists, therefore, for a means that reduces the amount of force that a user must apply to the deformable housing to achieve rupturing of the ampoule.
Glass shards may cut through the vinyl housing and cut a user's finger or thumb when the ampoule is broken. Thus, there is a need for an improved detector structure that reduces the chances that a user will be cut when crushing the ampoule.
A user may also ingest or inhale indicator reagent by breathing inwardly instead of exhaling when using the Paul device. A need therefore exists for an improved detector structure that ensures that no user will be able to ingest or inhale the indicator reagent even if the detector is improperly used.
Visual inspection of the indicator reagent may fail to detect color changes in the indicator reagent because the Paul detector is made primarily of clear materials. The housing is typically formed of clear vinyl and the ampoule is formed of clear glass. Depending upon the amount of background clutter that exists in the ambient environment, a color change may be undetectable. There is a need, therefore, for a way to frame the indicator reagent to enhance the effectiveness of a visual inspection. It would also be advantageous if a way could be found to increase the contrast between the reagent indicator and the background against which the reagent indicator is viewed.
Some indicator reagents turn into a first color when a first concentration of the tested-for substance is present, a second color when a higher concentration is detected, a third color when a still higher concentration is detected, and so on. Thus there is a need for a label containing information about the meaning of the various colors where a detector is provided with such a reagent.
There is also a need for a detector that provides a physical marker indicating whether or not gaseous fluid is flowing through the lumen of the detector.
In view of the fragile nature of the Paul detector, there is also a need for a substance detector that is protected from easy breakage so that it is truly portable.
A need also exists for a detector having no ampoule therewithin to reduce the cost of manufacturing and also to enhance the safety of the detector by eliminating the glass shards that are produced upon rupturing of an ampoule.
However, in view of the prior art considered as a whole at the time the present invention was made, it would not have been obvious to those of ordinary skill in the pertinent art that the identified needs were in existence nor would it have been obvious how to fulfill such needs if they had been identified.